In recent times, new transportation systems have been receiving attention as new transportation means other than buses and railroads. As one such new transportation system (an automated people mover or an automated transit system), a transportation system in which a vehicle having wheels formed of rubber tires runs on a track is well known.
A travel device of a vehicle having wheels formed of rubber tires is disclosed in, for example, the following Patent Document 1. The travel device of the vehicle disclosed in Patent Document 1 includes a pair of running tires, an axle configured to connect the pair of running tires, an axle support configured to support the axle, a suspension frame disposed at a front side or a rear side of the axle support and having a support section extending downward, upper and lower links configured to connect the support section of the suspension frame and the axle support, and an air suspension disposed between the vehicle body and the axle support.
The upper link and the lower link extend in parallel to each other in a horizontal direction, one ends of the links are connected to the support section of the suspension frame by pin coupling, and the other ends of the links are connected to the axle support by pin coupling.
In the travel device, a four-link parallel mechanism is constituted by the support section of the suspension frame, the axle support, the upper link and the lower link. Here, the axle support is relatively and vertically movably supported with respect to the suspension frame and the vehicle body, to which the suspension frame is attached, by the four-link parallel mechanism. In addition, in the travel device, vertical movement of the axle support according to vertical movement of the running tire and the axle due to the irregularity of a running road surface R are absorbed by the air suspension.
In addition, both of the upper link and the lower link extend in the horizontal direction when a vehicle is stopped in a state in which no passenger is present. Meanwhile, during running, when the vehicle enters the irregularity of the running road surface R, the axle support moves vertically according to vertical movement of the running tire and the axle. As a result, the upper link and the lower link are slightly inclined with respect to the horizontal direction. However, the inclination angle is about 0.5°, which means that the links substantially extend in the horizontal direction.